The Irradiation Shared Resource is a multi-instrument irradiation facility designed to provide high-quality irradiation and atomic absorption spectroscopy (AAS) service to NCCC cancer researchers at Dartmouth- Hitchcock Medical Center and Dartmouth College. This Shared Resource encompasses two ionizing radiation sources (137 Cesium and x-rays), and a Perkin-Elmer Model 2380 atomic absorption spectrophotometer equipped with a HGA4OO graphite furnace. The experimental irradiation of cells and rodents and the assay of serum and tissue cisplatin/carboplatin levels are principal services provided by the Resource. The ionizing irradiation and AAS components of the Irradiation Shared Resource have doubled the number of experimental irradiations and users since the previous submission in 1993. Approximately 30 NIH-funded projects used the Irradiation Shared Resource during the past year. The fiscal year l99~97 saw a four-fold increase (over any previous single year) in the number of cisplatin/carboplatin samples analyzed by the AAS component of the Resource. All these samples are related to NIH, in-house pilot, and/or collaborative corporate/academic cancer research projects. We have recently added a 2,500 sq. ft. laser laboratory facility to the Irradiation Shared Resource (no CCSG support for this component is requested). This additional laboratory, whiqh currently houses four medical-grade lasers, is located adjacent to the Cs irradiator facility; it more than doubles previous space occupied by the Irradiation Shared Resource. Once we have established a user and research track record for this facility, our goal is to incorporate the laser laboratory into a funded component of our Shared Resource.